Two asides here. Firstly, my students always seem to use the word racism to cover any kind of bigotry, whether racially motivated or otherwise. I put this down to poor vocabulary.
Secondly, we were encouraged earlier in the year to, instead of giving straight answers to such questions (or indeed, moving straight on from unusual answers), to first consider why the student might have said it in the first place and hopefully correct some subtle misunderstanding that might otherwise have been missed. Ie, we have been asked to try and consider the student's thought process before correcting them and moving on.

Me: (Pause) (Quite a long pause, because I couldn't work it out, though I did give it a good try)
Me: No.
A: Oh well Miss, it wasn't my question really you know, it was B's question, but when he asked it sort of...excited my curiosity Miss.
B: Yes, I just thought...well, you know....
Me: OK. No, they did not need to be lesbians. Being lesbians would not have helped their cause. The Suffragettes were fighting for the right to vote: therefore it did not matter with whom they were sleeping, because it hasn't got anything to do with getting the vote. Do you see?
A and B: Oh yes, Miss, OK, we understand.

So, now, the only link I can make is that someone has, at some point, told B that if feminists really wanted to be feminists they should be lesbians; or that all feminists are lesbians, or something. And now I feel I have to plan a lesson on feminism*. Also, because later on in the lesson somebody else asked why the Suffragettes didn't use sexual favours to win themselves the vote (though not in quite such a bald way as I have phrased it). What can I say? The hormones, they are raging. The whole class sniggered when I told them to turn to page 69.

I think secondary school textbooks should be printed without a page 69.

* Girl A will love that. Her sincerest wish after today's lesson was that she could go back in time so she could join the Suffragettes. I think she is awesome.